Energy and Environmental Aspects of Using Corn Stover for Fuel Ethanol

Abstract

SummaryCorn stover is the residue that is left behind after corn grain harvest. We have constructed a life-cycle model that describes collecting corn stover in the state of Iowa, in the Midwest of the United States, for the production and use of a fuel mixture consisting of 85% ethanol/15% gasoline (known as "E85") in a flexible-fuel light-duty vehicle. The model incorporates results from individual models for soil carbon dynamics, soil erosion, agronomics of stover collection and transport, and bioconversion of stover to ethanol.Limitations in available data forced us to focus on a scenario that assumes all farmers in the state of Iowa switch from their current cropping and tilling practices to continuous production of corn and "no-till" practices. Under these conditions, which maximize the amount of collectible stover, Iowa alone could produce almost 8 billion liters per year of pure stover-derived ethanol (E100) at prices competitive with today's corn-starchderived fuel ethanol. Soil organic matter, an important indicator of soil health, drops slightly in the early years of stover collection but remains stable over the 90-year time frame studied. Soil erosion is controlled at levels within tolerable soil-loss limits established for each county in Iowa by the U.S. Department of Agriculture.We find that, for each kilometer fueled by the ethanol portion of E85, the vehicle uses 95% less petroleum compared to a kilometer driven in the same vehicle on gasoline. Total fossil energy use (coal, oil, and natural gas) and greenhouse gas emissions (fossil CO 2 , N 2 O, and CH 4 ) on a life-cycle basis are 102% and 113% lower, respectively. Air quality impacts are mixed, with emissions of CO, NOx, and SOx increasing, whereas hydrocarbon ozone precursors are reduced.This model can serve as a platform for future discussion and analysis of possible scenarios for the sustainable production of transportation fuels from corn stover and other agricultural residues.

Exploring impacts of process technology development and regional factors on life cycle greenhouse gas emissions of corn stover ethanol

“…If the stover supply from one county is not sufficient for the NREL 2011 design (700,000 t/year), additional stover is assumed to be provided from neighbouring counties. Corn stover is assumed to be harvested in a second pass through the field (Sheehan et al, 2004). The corn stover is harvested, collected, preserved and stored in square and round bales.…”

“…Life cycle studies have evaluated lignocellulosic ethanol production from a variety of feedstocks including: corn stover, switchgrass, hybrid poplar, alfalfa and reed canary grass (e.g., Sheehan et al 2004;Spatari et al 2005;Kim and Dale, 2005;Adler et al, 2007, GonzalezGarcia et al, 2010Wang et al 2012). The studies examined the production and use in road transportation vehicles of ethanol/gasoline blends in the forms of E10 (10 vol% ethanol), E85 (85 vol% ethanol), and E100 (100% ethanol).…”

“…There are a number of LCAs of the corn stover to ethanol process (e.g., Sheehan et al, 2004, Luo et al, 2009, Hsu et al, 2010, Spatari and MacLean, 2010, Kaufman et al, 2010. These studies all reported that replacing gasoline with ethanol produced from corn stover would reduce GHG emissions; however, the percentage reductions (compared to gasoline) reported in the studies vary between 58% and 106%.…”

“…Hsu et al(2010), Spatari and MacLean (2010) and Kaufman et al (2010) used US-average data for corn yield, fertilizer application rate and electricity grid intensity. Sheehan et al (2004) determined the aforelisted data based on a specific location in Iowa. These studies did not include the impact of geographical variation on their LCA results, and did not distinguish between different stover harvesting requirements and biorefinery locations.…”

Safety, health, and environmental assessment of bioethanol production from sugarcane, corn, and corn stover

“…The process design trends of energy production from different kinds of bioresources have been reviewed [2,3] and technoeconomic analysis has been performed for the state-of-the-art and future pretreatment and conversion technologies [4], including the international transport for bioenergy supply chains [5]. The environmental impact, mainly expressed as greenhouse gases emissions, has also been evaluated for bioethanol production from various feedstock, including corn in the USA [6][7][8][9], sugarcane in Brazil [10,11] and corn stover [12,13]. Additionally, the issues of biomass availability [14] and water and land use [15,16] have also been studied.…”